1. Field of the Invention
This invention relates to filter units for use in a swimming pool water purification system and particularly to filter units which incorporate a disposable filter media in cartridge form.
2. Description of the Prior Art
The use of a filtering device to remove impurities from swimming pool water on a continuous basis has long been known.
One such filter unit utilizes a support surface made of a porous material on which a coating of diatomaceous earth is applied by adding the diatomaceous earth to water entering the filter unit. The diatomaceous earth forms a filter media over the porous support surface and collects solid impurities as water flows therethrough. Upon the coating of diatomaceous earth becoming contaminated with sufficient solids, the support surface is removed and sprayed with a typical garden hose to wash the diatomaceous earth therefrom. Another application of diatomaceous earth is then applied in the similar manner noted above.
Another type of filter in common use today includes a tank in which various grades of gravel and sand have been built up in progressive layers to form a filter media. As swimming pool water is circulated through this type of filter, solid impurities collect within the filter media. Such a filter is cleaned by backwashing or reversing the direction of flow through the filter which dislodges the collected solids which are then discharged into a municipal sewer or allowed to drain out on the swimming pool owner's lawn.
A third type of filter includes a tank having a readily removable cover providing access to a plurality of nonwoven polyester fiber filter modules. The number of filter modules within a particular tank is dependent on the volume or capacity of swimming pool water to be filtered in a particular time period. Each filter module is constructed of a nonwoven polyester fiber hermetically sealed at each end with noncorrosive urethane end caps.
Another filter unit utilizing a cartridge filter element for commercial and residential swimming pools includes a tank in which there are three cartridges comprising a filter media of a pleated material of polyester and cotton fibers reinforced with a cellulose mixture.
In still another filter unit designed to utilize a filter cartridge in which water enters a filter tank through a bottom inlet and flows upwardly about a filter cartridge having a pleated filter media made of a fabric. Water flows through the pleated media entrapping suspended solids on the surface of the fabric while allowing the resultant filtered water to travel down a center core of the cartridge and out of a bottom discharge.
A further cartridge filter according to U.S. Pat. No. 3,988,244 has a dome-shaped cover removably sealed to a base. The base includes an inlet which directs swimming pool water up a hollow center portion of a pleated filter element. The filter element is cylindrically-shaped and has a porous center collection core within the element. The collection core allows water to flow from inside and outside of the filter element to the collection core and to flow downwardly to pass therefrom to a discharge located in the base.
Replacement filter cartridges are available including a pleated filter media and a rigid center core to prevent bending or deforming of the cartridge in the middle which may allow internal bypassing of the filter media.
Nevertheless, improvements in such filters are still desirable. For example, there has been need for a simple, easily cleanable filter construction especially adapted for swimming pool use which will prevent solids not held on the filter medium from entering the water circulation system when the filter is being serviced for cleaning or replacement of the filter medium. Another area of desirable improvement is to simplify the selective use of from one to a plurality of similar units in any given system depending upon the filtration capacity requirements rather than simply providing a larger unit when greater capacity is needed.